1. Field of the Invention
This invention relates, generally, to surgical tools. More particularly, it relates to an apparatus that implants radioactive seeds into a prostate gland or other internal organ.
2. Description of the Prior Art
Surgical removal of the prostate, known as radical prostatectomy, became the treatment of choice for prostate cancer in the 1960s. The possible side effects of this procedure include loss of bladder control and impotence.
The percentage of patients who experience loss of impotency has been reduced in recent years by a new technique known as "nerve sparing radical prostatectomy." As its name implies, this procedure also includes the surgical removal of the prostate.
A nonsurgical mode of treatment, external beam radiation, has been used since the 1950s. This procedure produces lower rates of incontinence and impotency, but sometimes causes rectal problems since the rectum is radiated by the beam as well.
Still lower rates of incontinency and impotence result from the latest therapy, known as interstitial brachytherapy or radioactive seed implanting. In this technique, a predetermined number of radioactive pellets, known as seeds, that are about the size of a grain of rice, are implanted into a patient's prostate. In this way, radiation of the rectum and other organs near the prostate is minimized and such minimization, of course, reduces the risks of side effects.
There are two known methods for implanting the seeds. In the first method, a preloaded needle is used. A conventional luer lock eight inch needle is hand-loaded with seeds and spacers in the operating room. Seeds, and the spacers between them, can be easily dropped and any dropped seed must be found before the needle-loading procedure may continue; this is a rule mandated by the Nuclear Regulatory Commission, a federal agency charged with ensuring safe handling of radioactive devices, among other duties. After the needle is properly positioned in the prostate in accordance with a well-known procedure that need not be repeated here, a stylet, having a diameter smaller than that of the needle, is inserted into the needle behind the seeds and the spacers. The needle is then withdrawn over the stylet which remains in place; in this way, the seeds and spacers are constrained to remain in the prostate as the needle is withdrawn. The stylet is then withdrawn and the seeds and spacers remain in the prostate, the former to emit tumor-killing radiation and the latter as inert matter that does not interact with surrounding tissue.
An improved version of this procedure includes a plurality of seeds that are strung together by suture material, something like linked sausages. Thus, a string of seeds is inserted into the needle, thereby eliminating individual seed and spacer loading, greatly reducing the time it takes to load a needle, and essentially eliminating the problem with dropped seeds. The linked seeds are delivered in the same way, i.e., a stylet is placed behind the string in the needle and the needle is withdrawn from the prostate over the stationary stylet. The suture material eventually dissolves. The primary drawback of this procedure is that it requires continual reintroduction of seed strings as the procedure is performed. The number of seeds varies from patient to patient, but is usually between 40-100, with 70 being an average. Thus, in most cases, multiple strings are needed.
A device that includes a plurality of individual seeds in a artridge, known as the Mick (trademark) applicator system, after its inventor, is now in widespread use. The cartridge holds a large number of individual seeds which are loaded thereinto at a remote facility. the seeds can also be loaded into the cartridge at the hospital or at a nuclear pharmacy. This eliminates the time and cost of loading individual seeds in an operating room, eliminates the cost of manufacturing strings of suture-connected seeds, and eliminates the need to reload a needle with seed strings.
A seed-containing cartridge is attached to an applicator, in substantially the same way a magazine is attached to a weapon; the cartridge is spring-loaded to urge one seed at a time into a seed discharge chamber that holds a single seed at a time. A special hollow needle is connected to the leading end of the applicator. A plunger rod is inserted into a trailing end of the applicator and pushed forwardly, i.e., in a trailing-to-leading direction. The leading end of the plunger rod engages a seed in the seed discharge chamber and drives the seed into the hollow interior of the special needle and then out of the leading end of the needle into the prostate. The surgeon then withdraws the needle a predetermined distance, withdraws the plunger rod to a location on the trailing side of the seed discharge chamber so that another seed can enter the chamber from the cartridge, and that seed is then introduced into the prostate in the same way.
The grid system employed by physicians to ensure that the seeds are well-distributed throughout the prostate need not be described here because it is well-documented in the medical literature and forms no part of the invention described hereinafter.
The Mick applicator system decreases the amount of time required to implant a large plurality of seeds in a prostate and eliminates the risk of dropping individual seeds in an operating room. However, the system costs about $5,000.00, in part because the applicator is made of stainless steel, in part because the cartridge is machined and also made of stainless steel, and in part because the Mick system uses special needles that are reusable but which become dull as a result of such reuse.
The stainless steel components of the Mick applicator system are reusable because they can be disassembled, cleaned and then autoclaved. However, since the cartridge is not transparent, the number of seeds left therein cannot be easily ascertained unless the beginning number of seeds is known and the seeds are counted as they are implanted.
Thus, there is a need for an improved applicator system that is less expensive than the Mick applicator system, and which enables a surgeon to visually ascertain the number of seeds within a cartridge.
The Mick applicator system also has a utilitarian appearance that can be intimidating until a surgeon acquires familiarity with it. Thus, there is also a need for an interstitial brachytherapy applicator system having a physician-friendlier appearance.
Due to the expense of the Mick applicator system, it must be disassembled, cleaned, autoclaved and reused. Cleaning the nooks and crannies within the instrument is very difficult and time consuming. Autoclaving is also time-consuming and requires surgical procedures to be scheduled at long intervals. Built up blood and organic material can cause the spring loaded ball seat to freeze open, allowing a cartridge to fall out of the applicator if inverted. Thus, there is a need for a disposable interstitial brachytherapy device so that no time need be lost between patients.
However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how an improved applicator system could be provided.